Trouble getting level 1 techs to find root cause

I usually have issues with the first few people that answer the phone in the call center. I guess it's probably partly because I have EPON (not RFoG) and I was under the impression there are not alot of deployment like this.

The last couple days I've noticed performance issues here and there. I fired up ping plotter to see if I could see where the issue was happening. I could see high packet loss at both the inside of my CPE as well as the first hop into Comcast's network. I tried power cycling the CPE and replaced the patch cable going to the CPE. None of my trouble shooting steps changed anything. When I called the support line they said everything looked good and was a client device issue. I have tried about a dozen different devices both wired and wireless with the same symptoms.